1. Field of the Invention
The present invention relates generally to implantable devices, such as stents. More particularly, the invention relates to an implantable device having a modified surface and a method of modifying the surface.
2. Description of the Background
Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessel, such as by employing a stent. Stents act as scaffoldings, functioning to physically hold open and, if desired, to expand the wall of the passageway. Typically stents are capable of being compressed, so that they can be inserted through small lumens via catheters, and then expanded to a larger diameter once they are at the desired location.
Stents can be coated with various materials so as to provide therapeutic benefits in the treatment of an occluded vessel. For example, a stent can be coated with materials that provide the stent with increased biocompatibility, with lubrication for ease of positioning, with radiopacity or radioactivity for visualization, and with drug delivery capabilities.
It has been reported that coronary artery stents coated with titanium nitride oxide reduce neointimal hyperplasia in the porcine restenosis model. (Stephan Windecker et al., “Stent Coating with Titanium-Nitride-Oxide for Reduction of Neointimal Hyperplasia,” Swiss Cardiovascular Center, University Hospital, Bern, Switzerland.) Neointimal hyperplasia generally refers to vascular smooth muscle cell migration and proliferation in response to an injury caused by intravascular interventions such as stenting. It is believed that neointimal hyperplasia contributes, at least in part, to restenosis, which is the re-narrowing of the vessel within weeks or months following intravascular treatment. Blood vessels in which significant restenosis occurs typically require further treatment. Accordingly, it is desirable to minimize neointimal hyperplasia and restenosis.